IL-27 was identified as a cytokine with anti-HIV properties acting via similar although distinct pathways from those used by interferon-alpha. Cessation of antiretroviral therapy was found to diminish but not completely suppress the increases in CD4 T cells that are seen with IL-2. This finding was complemented by the discoveries that the increases in CD4 counts seen with IL-2 are correlated with changes in the state of baseline activation and that one can see increases in CD4 counts with IL-2 in patients who have never received antiretrovirals.